Urban Waters Federal Partnership – Groundwater and Surface Water Characterization of the Lower Gila River for the Rio Salado Project

The mission of the Flood Control District (FCD) of Maricopa County is to help reduce the risk of flooding to the public and their property. In support of efforts to reduce the recently re-delineated floodplain along the Gila River, FCD prepared the El Rio Vegetation Management Plan (Plan). The Plan was developed to identify areas to remove salt cedar and revegetate with native riparian and upland plant species (i.e., vegetation management). Removing salt cedar from the river corridor and replacing it with native vegetation will help prevent salt cedar from growing back and may reduce the extent of the floodplain.  Removal will also help to improve ecosystem function, which in turn should improve water quality. To better identify areas for vegetation management and to determine the types of native vegetation the area will support, it is important to understand the current salinity conditions and how they change with season, hydrologic conditions, and management practices. In addition to understanding the water-quality conditions, the fluctuations in groundwater elevation as well as the surface water availability is important to successfully reintroduce native riparian vegetation.

The purpose of this study is to provide water-quality information, gain an understanding of surface and groundwater interactions, and quantify salinity through water sampling and continuous monitoring of specific conductance, surface water, and shallow groundwater level fluctuations. The Plan calls for water-quality information related to salt cedar removal and native plant revegetation to be collected within the floodway along a 10-mile segment of the Lower Gila River that has been identified as potential habitat for important avian species like the Yuma Ridgway's Rail.  This reach includes the Gila River reach upstream of the confluence with the Waterman Wash to downstream of the State Route 85 bridge.

The data collection and monitoring activities will provide the FCD and other entities with information needed to adjust vegetation restoration approaches. The characterization of salinity in surface water and shallow groundwater will allow FCD and other entities conducting vegetation management to improve planting techniques, channel design, and salinity mitigation practices to control the resurgence of salt cedar.

Site locations shown on interactive study area map